After looking at some of the posts I think you guys might have an answer to my problem. First, even though I'm not totally ignorant to the ways of the Civic, treat me like I am. Some of the other posts contained abbreviations I wasn't able to decipher.

So here is the problem:
My '91 Civic (3dr hatch, manual trans, 1.3L?) infrequently idles in a "see-saw" fashion. I don't have a tach, but I'd guess it goes up and down between 5/600 and 12/1300 rpm. Sometimes it will idle low for awhile then idle high for awhile. Other times it will immediately rev after hitting a low idle point, and immediately descend after peaking. The problem seems to exacerbate during the warm months (I live in the NE USA), and after/during much stop-and-go traffic.

The only thing I can do to get it to stop is to tap the accelerator. That usually will smooth out the idling at 900-1000 rpm. The throttle cable has been checked and re-lubed - so that isn't the problem. I also had a tune-up done about a year ago (the problem has been ongoing for at least 3 years). On another site, a poster recommend I bleed the coolant system for air bubbles. I haven't done it yet as I'm pretty sure that would have been taken care of during the tune up (but I haven't ruled that out!). I keep my fuel injector clean. Also I recently had a new (forgive me) oxygen pump(?)-thing replaced.

I have talked with other Honda owners who have had similar problems with their Accords and Preludes - but no one has an answer. Any ideas? Thanks.

 

Check for a vaccum leak.
Get a bucket of water and dip you hand in it and run it over the lines....see if you can see/feel bubbles or air.